Create a scanline decoder without creating a codec

Prior to this CL, if a client wanted to decode scanlines, they had to
create an SkCodec in order to get an SkScanlineDecoder. This introduces
complications if input data is not easily shared between the two
objects.

Instead, add methods to SkScanlineDecoder for creating a new one from
input data, and remove the creation functions from SkCodec.

Update DM and tests.

Review URL: https://codereview.chromium.org/1267583002

1 files changed, 17 insertions, 11 deletions

diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index d1d9be030f..f555b9fcbd 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -159,11 +159,13 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
             break;
         }
         case kScanline_Mode: {
-            SkAutoTDelete<SkScanlineDecoder> scanlineDecoder(codec->getScanlineDecoder(
-                    decodeInfo, NULL, colorPtr, colorCountPtr));
-            if (NULL == scanlineDecoder) {
+            SkAutoTDelete<SkScanlineDecoder> scanlineDecoder(
+                    SkScanlineDecoder::NewFromData(encoded));
+            if (NULL == scanlineDecoder || SkCodec::kSuccess !=
+                    scanlineDecoder->start(decodeInfo, NULL, colorPtr, colorCountPtr)) {
                 return Error::Nonfatal("Cannot use scanline decoder for all images");
             }
+
             const SkCodec::Result result = scanlineDecoder->getScanlines(
                     bitmap.getAddr(0, 0), decodeInfo.height(), bitmap.rowBytes());
             switch (result) {
@@ -222,8 +224,11 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
                     const int y = row * subsetHeight;
                     //create scanline decoder for each subset
                     SkAutoTDelete<SkScanlineDecoder> subsetScanlineDecoder(
-                            codec->getScanlineDecoder(decodeInfo, NULL, colorPtr, colorCountPtr));
-                    if (NULL == subsetScanlineDecoder) {
+                            SkScanlineDecoder::NewFromData(encoded));
+                    if (NULL == subsetScanlineDecoder || SkCodec::kSuccess !=
+                            subsetScanlineDecoder->start(
+                            decodeInfo, NULL, colorPtr, colorCountPtr))
+                    {
                         if (x == 0 && y == 0) {
                             //first try, image may not be compatible
                             return Error::Nonfatal("Cannot use scanline decoder for all images");
@@ -289,9 +294,9 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
             const int numStripes = (height + stripeHeight - 1) / stripeHeight;
 
             // Decode odd stripes
-            SkAutoTDelete<SkScanlineDecoder> decoder(
-                    codec->getScanlineDecoder(decodeInfo, NULL, colorPtr, colorCountPtr));
-            if (NULL == decoder) {
+            SkAutoTDelete<SkScanlineDecoder> decoder(SkScanlineDecoder::NewFromData(encoded));
+            if (NULL == decoder || SkCodec::kSuccess !=
+                    decoder->start(decodeInfo, NULL, colorPtr, colorCountPtr)) {
                 return Error::Nonfatal("Cannot use scanline decoder for all images");
             }
             for (int i = 0; i < numStripes; i += 2) {
@@ -323,9 +328,10 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
             }
 
             // Decode even stripes
-            decoder.reset(codec->getScanlineDecoder(decodeInfo, NULL, colorPtr, colorCountPtr));
-            if (NULL == decoder) {
-                return "Failed to create second scanline decoder.";
+            const SkCodec::Result startResult = decoder->start(decodeInfo, NULL, colorPtr,
+                                                               colorCountPtr);
+            if (SkCodec::kSuccess != startResult) {
+                return "Failed to restart scanline decoder with same parameters.";
             }
             for (int i = 0; i < numStripes; i += 2) {
                 // Read a stripe